The present invention relates, in general, to hand brake assemblies for use on railway type vehicles and, more particularly, this invention relates to an apparatus to automatically activate and apply the brakes on such railway vehicle without requiring an operator to manually wind the chain on such hand brake.
Railway car hand brake mechanisms for applying at least one brake member secured to a railway vehicle in an emergency condition are well known in the art. U.S. Pat. Ser. No. 4,368,648 titled xe2x80x9cHand Brake for Railroad Carxe2x80x9d teaches such a hand brake having a quick release mechanism. They usually include a large, rotatable hand wheel disposed in a vertical plane and mounted on a drive shaft which, through a gear train, can rotate a chain drum to wind up a chain that is secured at its end remote from the chain drum to the brake member of the railway car. As the hand wheel is rotated in one direction, the brakes are applied and rotation of the hand wheel drive shaft in the opposite direction is prevented by a pawl which engages a detent ratchet on the hand wheel drive shaft.
The brakes may be released by disengaging the pawl from the detent ratchet but this causes rapid rotation of the hand wheel and the gears of the gear train. To avoid rapid rotation of the hand wheel, hand brake mechanisms have been devised which are known as xe2x80x9cquick releasexe2x80x9d mechanisms.
Generally these quick release mechanisms include a releasable connecting means between the hand wheel shaft and the gear train. When the connecting means is released, the gears of the gear train rotate rapidly, without constraint by the pawl and detent wheel, but the hand wheel remains stationary.
It has been generally known in the art that a new brake member of the railway vehicle requires a 13xe2x80x3 nominal chain take-up while 18xe2x80x3 of chain take-up represents a worst-case scenario of the brake member having worn brake shoes and excessive chain slack. The teachings of the U.S. Pat. Ser. No. 4,368,648 are hereby incorporated in present application by reference thereto.
The Association of American Railroads (AAR) specifies that the standard power hand brake mechanisms shall provide an average load on the chain of 3,350 lbs. with a 125 lb. turning force applied to the rim of a wheel twenty-two inches in diameter in order to set the brake.
Aforementioned application U.S. Ser. No. 10/217,570 teaches an automatic application set and release (ASR) hand brake apparatus, hereinafter referred to as ASR Design II hand brake, for automatically applying said at least one brake member. The apparatus comprises an operating member having at least one ratchet engageable with at least one gear of a gear assembly disposed in a housing member of the hand brake assembly for operating the gear assembly in a direction which will cause an application of the at least one brake member secured to a railway vehicle with the hand brake assembly. The apparatus also includes an application cylinder mounted on the railway vehicle and a drive arm extending from an end of the application cylinder. The drive arm has a first portion which is connected to the operating member. The drive arm is capable of reciprocating with respect to the application cylinder upon the application of a force thereto to supply a predetermined pressure to the operating member at least a sufficient amount so as to cause an application of the at least one brake member. A pressure supply source is connected to the application cylinder for supplying a force to the drive arm thereby causing an automatic application of the at least one brake member by the hand brake assembly.
While the ASR Design II hand brake has proven to be sufficient in achieving a vertical load on the chain of 3,350 lbs., the difficulties were encountered in maintaining said achieved vertical load for a long period of time. Based upon further data collected on the ASR Design II hand brake, it was determined that a load drop occurs over time, as the emergency reservoir pressure is dropping from the initial nominal setting, resulting in the average hold load falling below the requirement of 3,350 lbs.
As it can be seen from the above discussion, it will be advantageous to have an automatic application set and release apparatus for applying the hand brake which is capable of providing and holding the required average load on the chain of 3,350 lbs.
Generally, the brake pipe pressure in a railway vehicle is about 90 psi. In the emergency condition, after the main brakes have been applied, the pressure of the emergency reservoir equalizes at an average initial nominal setting of 78 psi for emergency hand brake application. The average initial nominal setting of 78 psi is, therefore, the maximum available pressure at which the ASR hand brake is required to achieve the required average load of 3,350 lbs. The ASR Design II hand brake with the improved pneumatic circuit as taught by the aforementioned application U.S. Ser. No. 10/201,888 has been set to operate with an average initial nominal pressure of 70 psi, providing operating margins for nominal pressure fluctuations. Said pneumatic circuit comprises control means connected to the source of fluid pressure for supplying and regulating said fluid pressure to the application cylinder and for stopping an automatic application of such brake means in case of the emergency or a reversal of the unintended activation.
Since recharging of the brake pipe pressure in the railway vehicle after a brake application requires a predetermined time period based on the pressure differential to be restored and, since, a typical train may consist of 150 railway vehicles, those of the ordinary skill in the art can easily see that it will be advantageous to employ ASR hand brake capable of achieving the required hold load with reduced emergency reservoir pressure in order to reduce the overall recharging period and, more particularly, to reduce the dwell time of the entire train consist due to recharging. It is further advantageous to improve the efficiency of the ASR hand brake and, more particularly, reduce the pressure drop within the operating means disposed within said apparatus as well as to reduce the size of the application cylinder.
An automatic application hand brake apparatus is provided for automatically applying at least one brake member secured to a railway vehicle with the hand brake assembly. The apparatus comprises a mounting bracket, an operating member having at least one ratchet attached to a drive shaft of said hand brake assembly externally of the hand brake assembly housing. The apparatus also includes an application cylinder connected to a drive arm pivotally attached to said drive shaft and containing and operating pawl engaging said operating ratchet. Said operating ratchet is rotating as a single unit with said drive shaft and a detent ratchet disposed within said hand brake assembly, thereby preventing partial unwindings of a chain winding gear of the hand brake assembly. A spring means are attached to said drive arm to urge said operating pawl toward said operating ratchet. A first and a second brass spacers are provided to substantially reduce friction during the rotation of said drive arm. The application cylinder is pivotally mounted on the mounting bracket enabling reduction of the application cylinder stroke. The reciprocating motion of the drive arm caused by the application cylinder enables reciprocal rotation of the operating arm and furthermore causing application of at least one brake member. A control means is connected to the source of the fluid pressure for initiating and regulating the supply of fluid pressure to the application cylinder. An additional control means is connected to the source of the fluid pressure for stopping an automatic application of such brake means in case of the emergency or a reversal of the unintended activation.
It is, therefore, one of the primary objects of the present invention to provide an apparatus engageble with a hand brake assembly which automatically activates and applies the brakes on a railway vehicle.
Another object of the present invention is to provide an apparatus engageable with a hand brake assembly on a railway vehicle which achieves and holds the required load for a standard power hand brakes.
A further object of the present invention is to provide an apparatus engageable with a hand brake assembly on a railway vehicle which provides a more efficient operation.
An even further object of the present invention is to provide an apparatus engageable with a hand brake assembly on a railway vehicle which utilizes smaller space envelope.
An additional object of the present invention is to provide an apparatus engageable with a hand brake assembly on a railway vehicle which provides an emergency shut-off means to stop automatic application of the hand brake.
In addition to the several objects and advantages of the present invention generally described above, various other objects and advantages of the invention will become much more readily apparent to those persons who are skilled in the relevant art from the following more detailed description, particularly, when such detailed description is taken in conjunction with the attached drawing figures and the claims appended hereto.